FIG. 1 depicts a holographic storage system, wherein the holographic storage system 100 includes: a signal beam 12, a data plane 14, a reference beam 16, a storage media 18, a data beam 22, and a detecting apparatus 20.
A light source, e.g. a laser light source, is split into two light beams by a beam splitter (not shown), one of the light beam is converted to the signal beam 12 after the light beam is emitted to the data plane 14, which means an image frame presented on the data plane 14 is also contained in the signal beam 12; and the other light beam is the reference beam 16. When the signal beam 12 and the reference beam 16 are both focused on the storage medium 18, an interference strip, which generated by the signal beam 12 and the reference beam 16, is formed on a focal point 24, wherein the interference strip can be regarded as a grating. When only the reference beam 16 is focused on the focal point 24 of the storage medium 18, the data beam 22 is generated and outputted from the extended direction of the signal beam 12. The image frame presented on the data plane 14 can be re-stored if the data beam 22 is received by the detecting apparatus 20 which is placed on the path of the data beam 22. In general, the storage medium 18 is a photopolymer.
A data-recording process in the holographic storage system 100 includes steps of: encoding the original data by a controlling circuit (not shown) and adding a correction code to the encoded data; converting the encoded data to an image frame and presenting the image frame on the data plane 14; converting a light beam to the signal beam 12 via emitting the light beam to the data plane 14; and recording the focal point 24, with an interference strip which is generated by the signal beam 12 and the reference beam 16, on the storage medium 18. By processing the above-mentioned steps, the original data can be converted to a plurality of image frames by the controlling circuit of the holographic storage system 100, and then the image frames can be recorded in the storage medium 18.
A data-reading process in the holographic storage system 100 includes steps of: focusing the reference beam 16 on the focal point 24 of the storage medium 18 to generate the data beam 22 outputted from the extended direction of the signal beam 12; placing the detecting apparatus 20 on the path of the data beam 22 for receiving the data beam 22 and presenting the image frame originally presented on the data plane 14 to the detecting apparatus 20; and decoding the image frame to the original data by the controlling circuit.
As the above statement, the recording holographic storage system at least includes: a laser beam source, a data plane 14, and a storage media 18. The read-only holographic storage system at least includes: a laser beam source, a storage media 18, and a detecting apparatus 20. The recording-and-reading holographic storage system at least includes: a laser beam source, a data plane 14, a storage media 18, and a detecting apparatus 20. Generally, the data plane 14 is a SLM (spatial light modulator), wherein the SLM can be a DMD (digital micro-mirror device) or a LCD (liquid crystal display). Both the DMD and the LCD are composed by a plurality of presenting units arranged as an array, and these presenting units with different intensities can present an image frame. In general, the each presenting unit is regarded as a pixel. The detecting apparatus 20 can be a CCD (charge-coupled device) or a CMOS (complementary metal oxide semiconductor), and both the CCD and the CMOS are also composed by a plurality of sensing units arranged as an array. The sensing units are use for receiving the image frame presented on the data plane 14, wherein the sensing unit is also regarded as a pixel.
In addition, when the detecting apparatus 20 receives the image frame contained in the data beam 22, a sensing signal is generated and outputted from each pixel according to the intensity received by the pixel. The intensity is representing a light state or representing a dark state will be further determined by the controlling circuit (not shown) processing the sensing signal. After all pixels on the detecting apparatus 20 representing a light state or a dark state are determined by the controlling circuit, the image frame can be rebuilt to the original data after the controlling circuit processing the decoding and correcting of the image frame data.
It is understood that a fail pixel may be contained in the data plane 14 or the detecting apparatus 20. Both the fail pixel contained in the data plane 14 and fail pixel contained in the detecting apparatus 20 can make the sensing signal outputted from the detecting apparatus 20 unable to be determined, so as the error rate of data recording or data reading may increase in the holographic storage system. Therefore, providing a method of detecting and compensating the fail pixels in the holographic storage system is the main purpose of the present invention.